Controls of the variations of individual and multiple ecosystem
functions following shrub encroachment
Plant cover, species richness, AGB and BGB were significantly related
with SW, NO3−−N and
NH4+−N contents (Fig. 5). The SOC and
STN contents also had significant relationship with BGB, SW,
NO3−−N and
NH4+−N. In pooled all data together,
we found that SR, AGB, SW, STN, MBC, and
NO3−−N had significant relationships
with the overall and above- and belowground ecosystem multifunction
indexes of the alpine steppes (Fig. 5). We further found that the RII
indexes of plant productivity, soil microbial biomass, and soil
nutrients had positive relationships with that of the ecosystem
multifunction indexes (Fig. 6), suggesting that plant productivity, soil
microbial activity, and soil nutrients play critical roles in driving
ecosystem functioning responses to shrubs encroachment (Fig. 7).
However, the RII index of EMF indicated that there were no significant
relationships between EMF and that of SR and SW (Fig. 6). For different
apart of the ecosystem functions, the RII indexes of AEMF and BEMF both
yielded positive and significant relationships with that of the plant
cover, AGB, BGB, SW, SOC, and NO3−−N
(Fig. 6).